Seems like I only post when I need help!
I've been running my SMTP server for quite a while now (a month) and I've noticed the following behaviour. Every now and then a client closes the socket during the DATA phase. I catch that and discard the message. However, after re-reading the RFC, I get 2 conflicting ways to handle this:
one part of the rfc states: 126.96.36.199 RESET (RSET)
... There are circumstances, contrary to the intent of this specification, in which an SMTP server may receive an indication that the underlying TCP connection has been closed or reset. To preserve the robustness of the mail system, SMTP servers SHOULD be prepared for this condition and SHOULD treat it as if a QUIT had been received before the connection disappeared.
ok, that says treat it as though a quit happened, which just doesn't sound right to me. If DATA was issued and I'm waiting to see a CRLF.CRLF, and the client closes the connection, I would think that it would be better to assume the entire message hasn't been sent.
however later I see:
188.8.131.52 QUIT (QUIT)
... If the connection is closed prematurely due to violations of the above or system or network failure, the server MUST cancel any pending transaction, but not undo any previously completed transaction, and generally MUST act as if the command or transaction in progress had received a temporary error (i.e., a 4yz response).
which doesn't quite make sense to me because basically it sounds like this:
DATA -> oops! -> back to MAIL state -> return a 4xx code but wait, the socket is closed!
So does anybody have some words of wisdom?
I'm thinking the correct behaviour is to treat it as the
client closed socket
server treats it as a RSET and QUIT.
I'm reachable at jeff @ virtualbuilder dot com